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Geological and other Reports

Wellington, January 1, 1864

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Wellington, January 1, 1864.

To His Honor
I. E. Featherston,
Superintendent of the Province of Wellington.


Since my report of April 13th, 1863, I have examined the south end of the Island, where it abuts upon Cook's Strait, and have also traversed various points in the Wairarapa and East Coast which I had not previously visited, including an ascent of the Aorangi range.

With the late additions, the traverses which I have made across the line of strike, in the East Coast country, now amount to six in number, and are as follows:

Round the shore from Wangamoana to the East Coast.


From the Huangarua river by Waipawa to Teawaite.


From Te puru puru, across the Wainuioro valley to the head waters of the Kaiwhata and thence to Waikaraka.


The high road from Masterton to Castle Point.


From Knight's station, at the foot of the Puketoi range, by the Tinui line, to the coast at the Whakatake river.


From the Ruataniwha plains to Porangahau, in the Hawke's Bay.

The latter examinations leave little for me to add to the views I have previously expressed, with regard to the East Coast rocks.

I find the old rocks to extend from Cape Palliser, in mass, as far north as the Pahaoa river—to the northward of this river they are only found in patches, overlaid by tertiary rocks, (as, for instance, high up in the Kaiwhata river), if we except a range running from the Huangarua river towards Hurunui orangi, which appears to be formed of old sandstones and slates.

These old rocks, from Cape Palliser northward, appear in general to be identical in lithological character with those of Tararua and Rimutaka, but I am not quite sure of this, for perhaps in some places they assume a different aspect, and the sandstones are also slightly calcareous.

The tertiary rocks, in these districts, fill up the vallies and cover the old rocks partially, or entirely, and it is often difficult to establish the exact line of demarcation.

I have, in a previous report, pointed out the rocks of the East Coast lying between the shore and the line of “taipos,” as of indeterminate age. I regret to say that, although I have found organic remains in them, these are of such faint and indistinct character, that the interesting question of their age must remain still unsettled.

These rocks consist of white limestones, more or less siliceous, in thin strata of from four to six inches thick, but cemented together so as to form a great thickness in the aggregate; they are alternated with sandstones with great regularity; there are also calcareous grits, cherts (probably altered from the calcareous, by the intrusive igneous rocks), sandstones showing carbonaceous markings, shales apparently carbonaceous, and there is also a rock, largely developed, coloured green and red, apparently by chlorite, or by epidote, which assumes every change from an apparent igneous rock to a sandstone.

These rocks may be Palæozoic, but as such they would hardly be likely to be so rich in carbonate of lime as they are; they may be tertiary, but then probably they would show their age by numerous fossils. In classing them as I propose to do I must mention that I am not satisfied as to their position with regard to the old rocks of Cape Palliser; greatly fractured, and dipping in various directions, this is a point difficult to determine.

Under the circumstances I will venture to put them down provisioually as Mezozoic, they are highly inclined and have evidently been forced into their present position by the intrusion of eruptive rocks. In the bed of the Kaiwhata river I found boulders of many varieties of igneous rock; amygdaloidal trap, basalt, hornblende rocks, &c., and at the Waihekino, about six miles south of Flat Point, I found reefs of the intrusive rock “in situ.”*

* Note.—Containing diallage, or bronzite.—W. B. C.

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I have also in the Wai-nui-oro, found boulders of more varieties of igneous rock, including porphyries, to the westward of the line of “taipos,” and at the Kahumengi a boulder of what appears to be trachytic porphyry, containing much iron pyrites.

I wish distinctly to point out that I do not include in the above named group of East Coast rocks, the various decided tertiary rocks that are found there, viz: The sandstones and mudstones with plant impressions, and small seams of brown coal, near Castle Point, &c.; a grey limestone at the slip panel on Mr. Barton's run containing ostrea; the fossiliferous reef at Castle Point, and various other limestones containing tertiary fossils.

I will now offer a few remarks on the newer tertiaries, which occupy the country from the Wairarapa to the “taipo” line (say seven miles from the East Coast.) The fossiliferous limestone which caps many of the ranges on the eastern side of the Wairarapa may be of about the same age as the “drift” gravel. I am inclined to think that in the period of the “drift” the land stood at a level of about 1000 feet below its present height, and that while the wearing away of the older rocks went on, which produced the crystalline sandstone gravel of the Wairarapa, the limestones, which are now at a height of 700 to 800 feet above the sea, might have been formed as reefs at a depth of 200 to 300 feet below the ocean level. I have never found this limestone, nor its underlying rocks; resting on the crystalline sandstone gravel, but there is much gravel derived from tertiary rocks, and soft deposit of mud, or marl, in the district above mentioned (and on which I think the limestone partly rests) frequently obscuring the stratification and almost always covering the “blue clay,” which in consequence, is seldom shown except in vertical sections. The calcareous marls of the hills bounding the Wairarapa on the East may be eventually of great use in fertilising the gravels of the Wairarapa.

The “blue clay,” sandstones and limestones of the above named district, generally dip slightly to the westward, probably tilted by the action of the eruptive rocks on the country towards the East Coast.

Having, as above, stated the result of my late observations on the East Coast rocks, I now propose to consider the Palæzoic rocks by the aid of the light thrown upon them by my old friend the Rev. W. B. Clarke.

In entering upon a geological enquiry as to the age of the rocks of this province, it soon became evident that the great interest centred upon the old and highly inclined rocks of the main range and its outliers, for, whereas the tertiaries which occupy so large an area of our surface are all more or less fossiliferous, and therefore it was a mere matter of time and comparison to ascertain their relative ages with regard to each other, hitherto the old rocks had yielded no organic remains of any description, and we were in consequence, totally ignorant as to their age. At the same time there was a sort of fixed opinion, among these who had considered the subject, and in which view I joined, that these rocks were Silurian, and therefore Graptolites, and other organisms of the Silurian age, were what were sought for.

However, as my enquiries proceeded, instead of characteristic Silurian organisms, impressions of plants were found, indistinct it is true, and without definite character, but still showing the presence of vegetation. I then discovered in many places thin seams of a black, coaly, looking subtance, and, particularly up the Otaki river, thicker seams of the same kind, with some faint impressions of plants, as also anthracitie looking slates. I saw that the “black mineral” looked very like coal, but remembered a dictum I had once heard of Sir Humphrey Davy's, that the primary tests for coal might be thus stated:—“Is it black and does it burn.” Now the black mineral that I had found would not ignite, even under the blow pipe, and the only reaction we could here obtain from was for iron. I was therefore obliged to send specimens to Australia for examination, and to wait for an opinion from that country.

With regard to these specimens, the Rev, W. B. Clarke writes as follows, on September 12th, 1863.

No. 37. Plant beds of Porirua {Like some beds in New South Wales coal field and also in England.
No. 40. Sandstone of Waikanae {A coarse quartzoze grit, probably a coal measure rock.
No. 54. Wai-o-taueru, Upper Otaki. {Calcareous quartzoze rock of the carboniferous formation. The black substance is coaly.page 5
No. 55, Gorge of Ruamahunga and 56. Wai-o-taueru, Otaki River. {Unmistakeable portions of a coal seam with coal. Similar patches of coal occur in the N.S.W. beds, where the coaly matter is traversed by lime threads. I consider this old, and perhaps the coal passes to anthracite.
No. 65. Oriental Bay. {Shale and sandstone of igneous materials from coal bed of same age, as No. 37, Porirua.
No, 69. Otaki river.—An altered rock of the coal beds.

“The occurrence of beds composed of what were once igneous materials, but since transmuted, are extremely common in the N.S.W. coal fields. Porphyritic grits; and fine conglomerates of almost granitic compounds are equally common. Near Scone, in the Upper Hunter district, such occur in Fig-tree Gully. At Prospect, in county Cumberland, and about Glen Alpin, near Campbeltown, and on the Paterson, rocks of this kind are very common, also in Illawarra there are like products.”

“The black substance which I examined before, illustrated by the new specimens, is quite in accordance with a substance of like kind near Wollongoug, which was reported to the Government here as graphite. It is from a bed of shale in the Mount Keera seams. On the whole, I consider this lot of specimens to justify the expectation of coal at the S.W. corner of the Province.”

The conclusion to be drawn from this report is, that the whole series of the rocks of these mountain ranges, with the exception of certain igneous rocks to be treated of in another place, may be “carboniferous,” From the plant beds of Porirua to those of Oriental Bay, from the “carboniferous” (?) grit of Waikanae to the black seams of the Rimutaka and the Wai-o-hine, from the coaly seams and the anthracitic looking slates of the Upper Otaki, to those of the gorge of the Ruamahunga, the report is constantly “carboniferous,” and from the number of different points at which the indications are found, we must, I believe include the whole of these rocks in one group, a most important point to establish.*

I had, in a previous report, adopted the view or the learned Professor McCoy, of Melbourne, that the plant beds of Porirua were of Mezozoic age, and was willing to suppose that they rested upon older rocks, but now that we are forced to class all the old rocks together, I must demnr to the Mezozoic view. At all events until the discovery of distinctive fossils, I shall class all these rocks as Palæozoic; from their position, and from their connection with the Eastern ranges of the Middle Island, I cannot do otherwise than describe them as such.

The plant impressions of Porirua and of Oriental Bay appear to be of marine origin, which perhaps increases the probability of a Silurian age for these rocks; but some of the organisms would appear to be terrestrial, or, at all events, semi-aquatic plants.

Having now arrived at the fact that our old rocks are carbonaceous in character, and possibly of “carboniferous” age, it remains to be seen what chances there are of finding workable coal seams amongst them.

Looking at the high inclination of the strata, and bearing in mind that we have hitherto been unsuccessful in finding coal seams of any consequence in traversing numerous sections across the line of strike, one would be inclined to decide this question in the negative; but there are reasons why we should not arrive at this conclusion too hastily.

In the first place, even in the line of the most exposed sections, there are large spaces covered by debris, or by forest, or otherwise so hidden from view that their strata cannot be spoken of with confidence. At the highest point, for instance, which I reached on the Wai-o-taueru, which falls into the Upper Otaki, the evidences of coal, or of carbonaceous substances, became very numerous, but here the cliffs of vertical strata, through which the river had hitherto cut its bed ceased, and the river ran over beulders, presenting no sections. In the ascent of the snowy range from this point no rock was found, except a few fragments thrown up in the roots of fallen trees.

* It will be perceived by and bye that the evidence, in favour of a “carboniferous” age must be modified; but I prefer to let the report stand unaltered, (even although it may appear somewhat contradictory), to show how necessary a careful chemical examination may be, to enable an observer to draw correct conclusions.

Certain fossils will be found described further on.

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Towards the centre of the range therefore, as elsewhere, coal seams may exist, but I believe that if they do, they are beyond the reach of the geological hammer, and will require a search with the pickaxe and spade.

It may be doubtful whether or not coal found vertical, or nearly so, would be of any practical value, but perhaps the first consideration should be to find the seams, the next to consider whether they can be worked.

If, however, all the carbonaceous seams, or veins, prove to be graphite instead of coal, the probabilities are that our old rocks are “Silurian,” or perhaps “Devonian,” and then, of course, a search for coal could not prove successful.

Before concluding my remarks on the Palæozoic rocks, I would observe, that in the great longitudinal valleys, such as those of the Hutt, the rivers appear to run in the line of the anticlinal “axes,'* whereas in the lateral valleys on both sides of the range, the river beds occupy mere cracks across the line of strike and may be said to have no true valleys while within the mountains, with the exception of a few inconsiderable terraces. In the place of valleys, there are mere ravines.

* Note.—From the broken character of the strata, a true line of axis is difficult to determine.

Note.—Dr. Haast makes particular mention of the beds of the Western rivers of Canterbury occupying anticlinal “axes.”